1. Field of the Invention
This invention relates generally to methods of contraception and prophylaxis against diseases transmittable by sexual contact and more particularly to a method using intravaginally administered lectins for contraception and to protect against the transmission of diseases that are transmissible by sexual contact and to treat such diseases. The invention also relates to a condom containing lectins.
2. Brief Summary of the Prior Art
Sexually transmitted diseases (STDs) are epidemic in this country and worldwide. Furthermore, other diseases that have not traditionally been considered to be STDs have also been found to be transmitted by sexual contact, e.g., hepatitis B. The medical and public health problems associated with these epidemics have motivated a search for methods of controlling these diseases by limiting their transmission from person to person. Similarly, although many methods of contraception have been employed, no universally satisfactory method has been developed.
Hitherto it has been generally agreed that barrier methods which prevent the transfer of body fluids between individuals are the most effective means of preventing transmission of such diseases. Such barrier methods are also effective contraceptive procedures. However, such methods are somewhat inconvenient and require some cooperation between individuals.
An example of a commonly used and generally effective barrier method is the use of condom by the male partner or of a similar barrier used by the female partner to provide complete isolation against transfer of bodily fluids from one partner to the other. Such devices are effective for prevention of transmission of STDs and for contraception, provided that the physical barrier remains intact. In some cases however, the condom or the like may develop microscopic leaks or may contain small and perhaps unnoticeable perforations which can permit the transfer of microorganisms or of sperm across the barrier. In other cases the condom may rupture and permit substantial transfer of bodily fluids with the consequence of possible infection or conception. Although gross rupture of a condom is relatively rare, it has been found that leaks sufficient to permit the escape of microorganisms in infectious amounts are by no means uncommon. Accordingly, the recent emergence of more serious and even fatal STDs such as AIDS has caused concern that even relatively reliable total barrier methods may not be satisfactory.
An alternative method for preventing the transmission of sexually transmitted diseases is to kill or inhibit the pathogenic microorganisms in semen and vaginal secretions so that they are incapable of infecting the tissues and causing the disease. While intravaginally placed spermatocides have been used for contraception, alone or in combination with barrier methods, antimicrobial materials have not been so used to prevent STDs, probably because many of such materials are irritating to adjacent tissues or are non-specific.
Administration of biologically active materials to the vagina for whatever purpose is usually accomplished by the use of some device that provides for convenient application of the medication by the user herself. A variety of devices exist for delivery of bioactive substances such as spermatocides and various medications. Each has its place in the medical armamentarium but each has certain deficiencies for application of contraceptive or anti-microbial agents in the context of sexual activity. Conventional vaginal suppositories and ovules may not provide medication to the entire vagina because of their shape and placement by the user in the vagina. Such suppositories are generally comprised of a material that melts at body temperature to allow the medication to spread and contact the tissues. However, when the dosage form melts, the medication may drain out of the vagina rather quickly, thus minimizing its potential effectiveness and significantly reducing the extended exposure of the tissues and pathogens to the medication which is often necessary for effective treatment. Similarly, the effective duration of contraceptives applied in this way tends to be relatively brief. In addition, such delivery vehicles, even when freshly applied, do not provide any physical barrier to deposition of male ejaculate on the cervix. Such ready access of sperm to the cervix may allow them to escape the action of spermatocides that are diffused throughout the vagina. Furthermore, because cells at the cervix are uniquely sensitive to several pathogens such as Chlamydia trachomatis, the absence of a barrier deprives these cells of a significant means of protection.
In order to provide for a longer retention of medication in the vagina and assure a more continuous delivery of active ingredients to the tissue, several types of vaginal rings have been proposed. Such devices are disclosed, for example, in Duncan, U.S. Pat. No. 3,545,439; Roseman, U.S. Pat. No. 3,920,805; Schopflin, U.S. Pat. Nos. 4,012,496 and 4,012,497; Wong et al., U.S. Pat. Nos. 4,237,885 and 4,286,587; and Nash et al., U.S. Patent 4,292,965. The vaginal rings are generally impregnated ith a spermatocide and are designed to be retained in the vaginal vault and to release the spermatocide slowly over a period of time to maintain an effective contraceptive concentration of the active material in the vagina. However, such devices do not prevent the direct contact of ejaculate with the tissues of the cervix, and therefore do not protect those tissues from contact with pathogenic organisms which might be contained in the ejaculate. They are also of questionable efficacy in supplying the spermatocide where it is most needed.
Another approach is to use a cervical cap or a diaphragm to serve as a mechanical barrier to the sperm and to dispense medication. These devices are designed for a relatively tight fit either to the cervix or the walls of the vagina to serve as a mechanical barrier to the passage of sperm. Such devices can be effective, especially as contraceptives and when combined with spermatocides. However, because of the need to provide a sperm-resistant seal they are frequently relatively complex devices incorporating metallic springs within a rubber or synthetic resin structure to provide the required sealing force.
Another approach to providing an effective concentration of spermatocide in the vagina is to provide a sponge impregnated with a spermatocide. Such applicators are not intended to be precisely located and may permit the contact of ejaculate with the tissues of the cervix, with the undesirable consequences outlined above.
Accordingly, a need has continued to exist for a method of contraception and prophylaxis against STDs by vaginal administration of a material that inactivates microorganisms or sperm and for a device that assures contact of such a material with microorganisms or sperm present in the male or female urogenital tract or male ejaculate.